chem questions for final

For the reaction indicated below, you observe the concentration of B2 and calculate the average rate of change to be -0.24 M/s. What is the average rate of change of [MB3] for the same interval of time (i.e., Δ[MB3]/Δt)? 2 MA2 + 3 B2 → 2 MB3 + 4 A

+0.16 M/s

7. show work: Calculate the cell potential, Ecell, for the redox reaction below at 25 °C if the concentrations are as follows: [Cu2+] = 0.100 M and [Fe3+] = 0.850 M. 3 Cu2+ (aq) + 2 Fe (s) → 3 Cu (s) + 2 Fe3+(aq) Eº = +0.304 V

+0.276 V

5. show work: Given the following pair of half reactions, what is the standard cell potential, Eºcell, for the spontaneous reaction? A2+(aq) + 2 e- → A(s) Eº = -0.59 V X3+(aq) + 3 e- → X(s) Eº = +1.08 V

+1.67 V

Assume that the following reaction is initially at equilibrium. Which of the following "stresses" would NOT cause a shift towards products? H2(g) + I2(s) ↔ 2 HI(g) ΔH> 0

- Increasing the volume of the system. - Removing some HI(g). - Adding more I2(s). - Adding more H2(g). - Raising the temperature.

In the following chemical reaction, which chemical acts as the Lewis acid? AlBr3 + NH3 ↔ Br3AlNH3

- NH3 - Br3AlNH3 - None of these species acts as a Lewis acid in this reaction. - AlBr3

The energy diagram below shows two different reaction pathways (A and B) for the same reaction. Which statement is incorrect?

- Pathway B represents a 1-step mechanism. - Pathway A represents the catalyzed reaction. - Pathway A represents a 2-step mechanism. - For Pathway A, Step 1 is the "rate-limiting" step of the mechanism. - The reaction is exothermic.

Which of the following statements about colligative properties is FALSE?

- Solutions remain liquid over a broader temperature range than the pure solvent. - The Kb and Kf values are designated for a solvent, independent of the solute. -Raoult's Law is used to predict the vapor pressure above a solution -Colligative properties may be used to determine the molar mass of a compound. - The predicted van't Hoff factor is always ≥ 2 for nonelectrolytes.

The solubilities of Compounds A and B (in grams per 100 g water) are shown in the figure below. Which of the statements is INCORRECT?

- The change in solubility with temperature for Compound B is nonlinear. - If 40 g of either compound was dissolved in 100 g water at 30°C, it would be an unsaturated solution. -The solubility of both compounds is identical at approximately 53°C. -The solubility of both compounds increases with increasing temperature. -If 35 g of Compound B was dissolved in 100 g of water at 20°C, it would be a supersaturated solution.

The evaporation of liquid water at room temperature (25 °C) and "ordinary" conditions is spontaneous despite the fact that the standard free energy change (ΔG°) for H2O(l) ↔ H2O(g) is positive. Which statement below explains why evaporation occurs at 25 °C?

- The endothermic phase change promotes the forward reaction. - The partial pressure of water in ordinary air is less than the equilibrium value. - Water is most stable in the gaseous state. - The energy given off promotes the forward reaction. - The decrease in entropy of the water promotes the forward reaction.

Which statement below regarding solubility is FALSE?

- The entropy increase due to mixing promotes the formation of a solution. - The solubility of a gas in a liquid decreases with increasing temperature. - A solution tends to form when strong interactions exist between the solvent and solute. - Most ionic compounds are miscible with water. - The solubility of a gas in a liquid increases with increasing partial pressure.

Based upon the titration curve shown below, which of the following statements is FALSE?

- The initial material (i.e., what is in the flask) is a weak base. - The initial pH of the material in the flask is ~11. - The material being titrated is monoprotic. - The two pKa values are approximately 10 and 5. - The titrant is most likely a strong acid.

Which of the following statements about a chemical system at equilibrium is FALSE?

- The reaction continues in both directions (i.e., forward and reverse). - There is no further "shift" in the reaction if it is left undisturbed. - The rate constants for the forward and reverse reactions must be equal. - The forward reaction rate and the reverse reaction rate must be equal. - The concentrations of all of the substances remain constant.

2. show work: For a redox reaction at standard conditions involving the transfer of 2 moles of electrons, the standard free energy change is: ΔG° = +217 kJ. Using this information, calculate the standard cell potential, Eºcell , for the reaction.

-1.12 V

8. show work: For the reaction below, ΔG° = -206.3 kJ. What is ΔG at 25ºC when the partial pressures of the reaction species are as indicated below? 2 XO(g) + O2(g) ↔ 2 XO2(g)Partial pressures (atm): 0.350 0.200 0.0100

-219.9 kJ

2. show work: What is the freezing point of an aqueous solution containing 12.7 g KNO2(MM = 85.11 g/mol) dissolved in 115 g of water? Kf = 1.86°C/m for water and assume "ideal" behavior (i.e., no ion-pairing).

-4.83 °C

Which of the following mixtures would result in a pH buffer solution?

0 mL of 1.0 M HF and 20 mL of 1.0 MHCl 40 mL of 1.0 M HF and 40 mL of 1.0 MHCl 40 mL of 1.0 M HF and 20 mL of 1.0 M NaOH 40 mL of 1.0 M NH3 and 20 mL of 1.0 M NaOH 40 mL of 1.0 M NH3 and 40 mL of 1.0 MHCl

8. show work: A button battery is based upon the redox reaction shown below. If the battery has a rating of 28 mAh, what mass of Ag2O is required? NOTE: Molar mass of Ag2O is 231.74 g/mol Ag2O(s) + H2O(l) + Zn(s) → 2 Ag(s) + Zn(OH)2(s) Eº = +1.591 V

0.12 g

5. Show Work: A specimen contains 2.5 g of a radioactive isotope with a half-life of 11.6 hours. What mass of the isotope remains after 2 days?

0.14 g

Indicate which aqueous solution has the lowest freezing point. NOTE: Assume no ion-pairing occurs.

0.2 m Na3PO4 0.3 m SrCl2 0.2 m K2SO4 0.3 m LiF 0.4 m KClO4

5. show work: The picture represents the molecules present at equilibrium for the reaction shown below. What is the value of KC for this reaction? A2(g) + B2(g) ↔ 2 AB(g)

1.1

5. show work: For some reaction, the activation energy, Ea, was measured as 12.6 kJ/mol. If the rate constant at 100 oC is 2.8 x 10-4 s-1, what is the rate constant at 300 oC?

1.2 x 10^-3 s^-1

4. show work: A solution has a pOH of 8.12. What is the value for [H3O+]?

1.3 x 10^-6 M

8. show work: What is the solubility of Ag3PO4dissolved into a solution which contains 0.600 M K3PO4? For Ag3PO4, Ksp = 8.89 x 10-17

1.76 x 10^-6 M

5. Show Work: Calculate Keq at 25 °C for a reaction with ΔG° = +67 kJ.

1.8 x 10^ -12

7. show work: Lab data for a reaction involving a single reactant, A, determines that a plot of ln[A] vs. time gives a straight line. Two of the experimentally measured concentration values are given in the table below. Use this information to calculate the rate constant, k, for this experiment. Assume 3 significant figures. Time (s) [A] (M) 35 seconds 0.752 115 seconds 0.168

1.87 x 10^-2 s^-1

Based upon the following properly balanced redox reaction, how many moles of electrons are transferred (i.e., what is the value of "n")? 10 HClO(aq) + 2 Mn2+(aq) → 5 Cl2(g) + 2 MnO4- (aq) + 2 H2O(l) + 6 H+(aq)

10

2. show work: The reaction below shows the combustion of a fuel which can be burned to produce energy. What is the maximum amount of energy you could derive from 4.75 g of CH3OH(l)? Molar mass of CH3OH(l) = 32.04 g/mole 2 CH3OH(l) + 3 O2(g) → 2 CO2(g) + 4 H2O(l) ΔG° = -1401 kJ

104 kj

3. show work: What is the pH of a 0.600 M solution of (CH3)3N? Kb = 6.4 x 10-5

11.79

What product nuclide would result from alpha decay of neodymium-144, 144^Nd?

140^Ce

2. show work: A 0.064 g sample of an organic compound (a nonelectrolyte) was dissolved in 4.8 g of CCl4 solvent. The freezing point of the solution was observed to be 2.7 °C lower than the normal freezing point of CCl4. If Kf = 29.9 °C/m, what is the molar mass of the compound?

150 g/mol

3. show work: A solution contains only hexane and chloroform. If the mole fraction of hexane is XHex = 0.614, what is the vapor pressure above the solution at 25°C? The vapor pressure of pure hexane is 151 mm Hg at 25°C and the vapor pressure of pure chloroform is 194 mm Hg at 25°C.

168 mm Hg

6. show work: What mass of Sn metal would be deposited onto a metal object during electroplating of a Sn2+(aq) solution for 45.0 minutes at a constant current of 1.25 A? Sn2+(aq) + 2 e- → Sn(s) Eº = -0.14 V

2.08 g

7. show work: At equilibrium, a reaction vessel is found to contain the indicated concentrations of O2 and ZO2. What is the corresponding concentration of ZO at equilibrium? 2 ZO(g) + O2(g) ↔ 2 ZO2(g) KC = 5.8 x 10^3 [ZO] = ??? M [O2] = 0.065 M [ZO2] = 0.45 M

2.3 x 10^-2 M

5. show work: A 65.00 mL solution initially contains 0.300 M HNO2 and 0.200 M KNO2. What is the new pH after 1.0 mL of 3.0 M HCl is added? Ka = 4.6 x 10-4

2.99

Which of the following reactions would be expected to have a positive ΔS?

3 H2(g) + N2(g) → 2 NH3(g) CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l) NaNO3(s) → NaNO3(aq) AgNO3(aq) + KCl(aq) → AgCl(s) + KNO3(aq) H2O(l) → H2O(s)

9. show work: A weak diprotic acid, H2A, has the following Ka values: Ka1= 3.6 x 10-6 and Ka2 = 5.8 x 10-9 . What is the pH of a 0.215 M solution of this acid?

3.06

10. show work: Given the following reaction and its equilibrium constant (KC) at 75°C, what is the value of KP for this reaction at the same temperature? AX(g) + 2 B2(g) ↔ AB4X(g) KC = 2.7 x 10-6 at 75°C

3.3 x 10-9

1. show work: Both 0.200 M HF and 0.250 M NaF are initially present in a 60.0 mL solution. What is the pH after 1.0 mL of 2.5 M KOH has been added? Ka = 6.8 x 10-4

3.43

10. show work: Use the table below to calculate the binding energy of one mole of lithium-7 nuclei (each with an exact mass of 7.016003 amu) in units of kJ. Species or Equation Exact Mass or Value 1 neutron - 1.00867 amu 1 proton - 1.00728 amu 1 amu - 1.66054 x 10-27 kg ΔE = (Δm)c2 c = 2.998 x 108 m/s

3.64 x 10^9 kJ

2. show work: The reaction shown below has a KCvalue of 5.2 x 10-7. Starting with an initial concentration of A2X4 of 0.400 M, what will the concentration of AX2 be when equilibrium is reached? A2X4(g) ↔ 2 AX2(g)

4.6 x 10^-4 M

6. show work: A radioactive isotope decomposes via first order kinetics. If the rate constant is 1.08 x 10-2 s-1, how long will it take for 39.2 % of the material to decompose?

46.1 s

What chemical species belongs in the blank shown below to balance this nuclear equation? 209Bi + ____ →262Bh + 1n

54 Cr

1. show work: Calculate the equilibrium concentration of Hg2+(aq) in a solution that is initially 0.100 M Hg(NO3)2 and 0.750 M KCl. The formation constant for [HgCl4]2-(aq) is Kf = 1.1 x 10 16.

6.1 x 10-16 M

1. show work: If the pH of a 0.760 M solution of a weak acid is found to be 1.18, what is Ka for the acid?

6.3 x 10-3

4. show work: 0.50 M XO is combined with 0.35 M O2 in a reaction vessel. Once equilibrium is reached, the XO2 concentration is 0.38 M. Calculate KC for the reaction below. 2 XO(g) + O2(g) ↔ 2 XO2(g)

63

9. show work: A sealed pop bottle is pressurized with CO2 at a partial pressure of 2.41 atm. If the Henry's Law constant for CO2dissolved in water at 25°C is kH = 3.4 x 10-2M/atm, what mass of CO2 would be dissolved in 2.0 L of pop?

7.2 g

1. show work: Given the equilibrium constant for the second reaction shown below, what is the value of the equilibrium constant for the first reaction shown below? A2(g) + 2 B2(g) ↔ 2 AB2(g) KC = ??? AB2(g) ↔ 1/2 A2(g) + B2(g) KC = 3.7 x 10-4

7.3 x 10^6

2. show work: For some reaction with a single reactant, A, the rate constant is k = 0.00493 M-1s-1. If [A]0 = 0.4600 M, how long will it take until [A] = 0.3900 M? HINT: Think about what the units of "k" tell you!

79.1 s

5. show work: What is the pH of a 0.750 M solution of KF? The Ka value for HF is 6.8 x 10-4

8.52

8. show work: A 18.9 mg sample of an organic compound was dissolved in water to produce 5.00 mL of solution at 25°C. The osmotic pressure of this solution was measured and found to be 0.106 atm. What is the molar mass of the compound? NOTE: Assume the compound is a nonelectrolyte.

8.72 x 10^2 g/mol

10. show work: 25.0 mL of 0.700 M HBrO is placed in an Erlenmeyer flask. After titrating the solution with 24.0 mL of 0.500 M KOH, what is the pH of the solution in the flask? Ka = 2.8 x 10-9

8.89

10. show work: Some solvent has a normal boiling point of 60 °C. What is the vapor pressure (in mm Hg) at 180 °C if the enthalpy of vaporization (ΔH°vap) for the solvent is +26 kJ/mol?

9.1 x 10^3 mm Hg

7. show work: What is the molality of an aqueous solution which is 5.75 M glycerol (MM = 92.094 g/mol) if the density of the solution is 1.11 g/mL?

9.91 m

6. show work: A reaction has the following standard enthalpy and entropy change values: ΔH° = -117 kJ and ΔS° = -396 J/K. For what temperature range would this reaction be considered "spontaneous"?

< 295 K

The graph below corresponds to a set of equilibirum constant values, K, measured at different temperatures. What type of reaction must this represent?

A reaction for which ΔH° < 0 and ΔS° < 0 A reaction for which ΔH° = 0 and ΔS° = 0 A reaction for which ΔH° > 0 and ΔS° < 0 A reaction for which ΔH° > 0 and ΔS° > 0 A reaction for which ΔH° < 0 and ΔS° > 0

Which of the following statements about radioactive decay products is FALSE?

Alpha particles have the highest penetrating power of nuclear decay products. An alpha particle is equivalent to a helium nucleus. A positron has the same amount of charge as an electron, but opposite in sign. Gamma rays have the lowest ionizing power of nuclear decay products. A beta particle is a high energy electron.

Which of these is the predicted order for INCREASING solubility (i.e., lowest to highest) in hexane, CH3CH2CH2CH2CH2CH3?

CH3CH2NH2 < CH3CH2CH2NH2 < CH3CH2CH2CH3

The following graph shows the kinetics curves for the reaction shown below. Which curve represents substance A? 5 A + B → 3 C + 4 D

Curve 1 Curve 2 Curve 3 Curve 4

Given the following standard reduction potentials, Eº, predict the principal substances produced at the cathode and anode when an aqueous solution of NiF2 undergoes electrolysis. Ni2+(aq) + 2 e- → Ni(s) Eº = -0.23 V F2(g) + 2 e- → 2 F-(aq) Eº = +2.87 V 2 H2O(l) + 2 e- → H2(g) + 2 OH- ( aq) Eº = -0.41 V (at pH=7) O2(g) + 4 H+(aq) + 4 e- → 2 H2O(l) Eº = +0.82 V (at pH=7)

H2(g) is produced at the cathode and O2(g) is produced at the anode. H2(g) is produced at the cathode and F2(g) is produced at the anode. Ni(s) is produced at the cathode and O2(g) is produced at the anode. Ni(s) is produced at the cathode and F2(g) is produced at the anode.

Which one of the following is not a conjugate acid-base pair? NOTE: Order written does not matter!

HF and F- HNO3 and NO3- HSO4- and SO42- H3O+ and OH- HCO3- and CO32-

Which of the following is expected to have the LARGEST standard molar entropy (S°)?

He(g) H2O(l) CO(g) N2(l) NO2(g)

Which of the following represents the ionization reaction (i.e., Ka) of a hydrated metal ion, M3+, in water?

M3+(aq) + 2 H2O(l) ↔ M(OH)2+(aq) + H3O+(aq)

The following species participate in a redox reaction. Which of the equations below represents the properly balanced reduction half-reaction in acidic solution? H2SO3(aq) + NO3- (aq) → SO42- (aq) + NO(g)

NO3- (aq) + 4 H+(aq) + 3 e- → NO(g) + 2 H2O(l)

Which one of the following salts does notproduce a basic solution when dissolved in water?

Na2S NaF NaClO3 NaBr Na3PO4

Which of the following chemical substances would INCREASE the solubility of Ca(OH)2(s) if it was added to a saturated solution in contact with excess solid Ca(OH)2?

NaOH(s) CaBr2(s) HBr(s) NaBr(s) Ca(NO3)2(s)

Which of the following statements regarding the voltaic cell described below is FALSE? Zn(s) | Zn2+(aq) || Ni2+(aq) | Ni(s)

Ni2+ ions are being converted to solid nickel at the anode. The single vertical line separates phases which are in contact with each other. The double vertical line represents the salt bridge. For the net redox reaction described, 2 moles of electrons would be transferred. Zinc metal is being oxidized to Zn2+(aq).

Which of the following is NOT an application of radioactivity?

Nuclear Magnetic Resonance Radiation Therapy Radiotracer Detection Radiocarbon Dating PET Scans

Which of the following statements about nuclear fusion is FALSE?

Nuclear synthesis reactions are examples of "transmutation". The target in nuclear synthesis reactions is the lighter reactant nuclide. The energy from the sun is create by nuclear fusion of hydrogen atoms. The "hydrogen bomb" is based upon a fusion reaction between deuterium and tritium. Linear accelerators are used to achieve the high velocities required for nuclear synthesis.

quiz 3 (ch 16)

Quiz 3 (ch 16)

A proposed mechanism for the following overall reaction is shown below: Overall: AX2 + 2 BY → AY2 + 2 BX Step 1: AX2 + BY → AXY + BX (Slow) Step 2: AXY + BY → AY2 + BX (Fast) What are the molecularities of Steps 1 and 2, and what is the correct expression for the rate law?

Step 1 Step 2 Rate Law unimolecular | bimolecular | Rate = k[AX2][BY]2 bimolecular | bimolecular | Rate = k[AX2][BY] unimolecular | bimolecular | Rate = k[AX2][BY] bimolecular | bimolecular | Rate = k[AXY][BY] bimolecular | bimolecular | Rate = k[AX2][BY]2

Based on the molecular structure, which of these pairs of acids is INCORRECTLY ranked (i.e., stronger vs. weaker)?

Stronger. Weaker HF H2O HNO3 and NO3- HSO4- and SO42- H3O+ and OH- HCO3- and CO32-

Which statement about a voltaic cell is NOT correct?

The electrodes are usually metal strips. In the external circuit (i.e., in the wire), electrons flow toward the cathode. Chemical species can have their oxidation number decreased at the cathode. Electrons are consumed at the anode. Reduction takes place at the cathode

Which nuclide of zinc would you expect to have a longer half-life: 56Zn or 60Zn?

The two half-lives should be the same. 60Zn would be expected to have a longer half-life. 56Zn would be expected to have a longer half-life. There is not enough information to answer this question.

If a solution of Pb(NO3)2(aq) is mixed with a solution of NaBr(aq), what condition would cause precipitation of PbBr2(s) to occur?

When [Pb2+][Br-] > Ksp for PbBr2. When [Pb2+][Br-] < Ksp for PbBr2. When [Pb2+][Br-]2 < Ksp for PbBr2. When [Na+][NO3-] < Ksp for PbBr2. When [Pb2+][Br-]2 > Ksp for PbBr2.

For some hypothetical weak acid, HA, which of the following pairs of concentration values would make a buffer with the largest buffer capacity?

[HA] [A-] 0.2 M 0.2 M 0.4 M 0.2 M 0.2 M 0.4 M 0.3 M 0.3 M

An equilibrium that strongly favors reactants has

a value of K << 1

What type of radioactive decay process is most likely to occur for oxygen-19, 19O?

alpha decay beta decay positron emission neutron capture gamma decay

The following figure shows Arrhenius plots for four different reactions. Which reaction has the largest frequency factor?

c

exam 1 (ch 14 and 15)

exam 1 (ch 14 and 15)

The rate law for a reaction involving 2 reactants (A & B) is 2nd order with respect to reactant A and zero order with respect to reactant B. If the concentration of A is increased by a factor of two and the concentration of B is decreased by a factor of two, the reaction rate will

increase by a factor of four.

quiz 1 (ch 14)

quiz 1 (ch 14)

quiz 2 (ch 15)

quiz 2 (ch 15)

quiz 4 (ch 17)

quiz 4 (ch 17)

quiz 5 (ch 18)

quiz 5 (ch 18)

quiz 6 (ch 19)

quiz 6 (ch 19)

quiz 7 (ch 20)

quiz 7 (ch 20)

quiz 8 (ch 21)

quiz 8 (ch 21)

9. show work: Given the following initial rate data, determine the rate law for the reaction. B2(g) + 2 AB2(g) → 2 AB3(g) Experiment [B2] (M) [AB2] (M) Rate(M/s) 1 0.100 0.100 6.79 x10-4 2 0.300 0.100 6.10 x10-3 3 0.300 0.200 6.12 x10-3

rate= k[B2]^2

What is the term used for the minimum amount of material needed to sustain a nuclear chain reaction?

threshold mass critical mass absolute amount limiting quantity least amount

CH3NH3+(aq) would be classified as a _________________.

weak acid